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Inhibition of protein synthesis in vitro by procollagen-derived fragments is associated with changes in protein
Abstract:
The NH2-terminal extension fragment (Col 1) of the pro alpha 1(I) procollagen chain selectively inhibits the translation of procollagen mRNA in a reticulocyte lysate system, whereas the reduced and alkylated fragment (AE-Col 1) and its proteolytically derived peptides inhibit the translation of all mRNAs (Hörlein, D., McPherson, J., Goh, S. H., and Bornstein, P. (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 6163-6167). The latter inhibitory function, which occurs at the level of polypeptide chain initiation, has now been shown to be associated with an increase in phosphorylation of an Mr = 94,000 protein. The time span required for observation of changes in phosphorylation and in inhibition of protein synthesis is similar. Since AE-Col 1 can serve as a substrate for casein kinase II, we suggest that phosphorylation of AE-Col 1 and its derivatives may be required for their activity.
Insights
The NH2-terminal extension fragment of procollagen selectively inhibits protein synthesis. Its modified form increases phosphorylation of a 94 kDa protein, suggesting this modification is key to its inhibitory activity.
Area of Science:
- Biochemistry
- Molecular Biology
- Cellular Regulation
Background:
- Procollagen synthesis involves translation of specific mRNAs.
- The NH2-terminal extension fragment (Col 1) of procollagen plays a role in regulating this process.
Purpose of the Study:
- To investigate the mechanism by which modified procollagen fragments inhibit protein synthesis.
- To explore the role of protein phosphorylation in this inhibition.
Main Methods:
- Utilized a reticulocyte lysate system to study mRNA translation.
- Analyzed protein phosphorylation changes using gel electrophoresis.
- Investigated substrate specificity of casein kinase II.
Main Results:
- The reduced and alkylated fragment (AE-Col 1) and its derivatives inhibit translation of all mRNAs at the polypeptide chain initiation level.
- This inhibition is associated with increased phosphorylation of an Mr = 94,000 protein.
- AE-Col 1 serves as a substrate for casein kinase II.
Conclusions:
- Phosphorylation of AE-Col 1 and its derivatives is likely required for their protein synthesis inhibitory activity.
- This suggests a regulatory role for post-translational modification in collagen synthesis control.